The standard [MIPI M-PHYSM Version 1.00.00—Aug. 2, 2011] characterizes a rapid communication interface between integrated circuits, in particular, between an analog integrated circuit of a radio receiver and a digital integrated circuit intended to perform the required processes on the received signal. The signals are transmitted between circuits in a low voltage differential form, called LVDS (Low Voltage Differential Signal).
FIGS. 1a and 1b show a typical startup of a transmission according to the MIPI M-PHYSM standard, and more particularly, an exemplary waveform of the two components R×P and R×N of the LVDS signal, respectively are shown. In the absence of activity, corresponding to the initial part of the waveform, the components R×P and R×N are both at zero. At the beginning of an activity, both components are brought to a same common mode level Vcm, typically around 200 mV. The components R×P and R×N then evolve in phase opposition, symmetrically with respect to the common mode Vcm, typically between 100 and 300 mV.
A transmission between an emitter circuit and a receiver circuit is generally discontinuous. Thus, to save energy, it may be desirable to activate the reception circuits only when the received signal has an activity. Indeed, a reception circuit consumes current even when the input signal is inactive. This consumption increases with the nominal frequency of the input signal.
There is therefore a need to detect an activity of an LVDS signal of the type of FIGS. 1a and 1b. Then, for example, the reception circuit may be powered up only during the phases where the signal has an activity.
Patent application WO2009117394 describes an approach to detecting the activity of an LVDS signal, independently of the common modes of the two signal components. The circuit described is particularly complex, in particular, if the activity indication signal should be delivered as a DC voltage. In addition, the current consumption of the circuit is high given the number of branches between the power supplies lines.